The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In a conventional refrigeration or HVAC system, flow control devices are typically utilized to control the flow of working fluids in a refrigeration system. In general, the refrigeration system would include a compressor that forces the particular refrigerant used in the system through a condensing coil, where the refrigerant vapor liquefies. The liquid refrigerant passes through a thermostatic expansion valve, expanding the high pressure liquid refrigerant to a low pressure vapor. The low pressure, low temperature refrigerant discharged from the thermostatic expansion valve is then directed through an evaporator coil for absorbing heat and thus refrigerating the space inside the container surrounding the evaporator coil.
The thermostatic expansion valve functions to meter the flow of refrigerant into the evaporator coil in proportion to the rate of evaporation of the refrigerant in the evaporator coil, and is responsive to the temperature and pressure of the refrigerant leaving the evaporator coil. In this manner, the thermostatic expansion valve is intended to control flow so that the refrigerant leaves the evaporator coil at a predetermined superheat. Generally, the superheat of the refrigerant is a measure of the heat contained in the refrigerant vapor above its heat content at the boiling point (saturated vapor temperature) at the exiting pressure. Maintaining the refrigerant entering the suction line from the evaporator coil at a desired superheat level enhances the refrigeration system performance.
Thermal expansion valves are typically used, in conjunction with a suction regulator, to maintain a consistent evaporator coil pressure. In known systems, conventionally designed mechanical pressure regulators are used for this purpose. Conventional mechanical pressure regulators include a throttling element that, when moved, limits the flow of the refrigerant through the suction regulator to regulate the pressure. A diaphragm, or other sensing element, responds to variations in the inlet pressure and moves the throttling element accordingly. A reference pressure, typically exerted by a spring, is applied to one side of the diaphragm to bias the diaphragm in a desired position, or set point. High side inlet pressure is applied to the other side of the diaphragm to move the diaphragm against the spring, and thus, move the throttling element.
In many refrigeration system implementations, finer temperature control is desirable. Adjusting the setting of conventionally designed mechanical pressure regulators in such thermal expansion valves can be a time consuming, manual process. Moreover, if the refrigerant or desired temperature changes, the complicated process of manually adjusting the pressure regulator's set screw must be repeated.